Can 48V Be the Auto Industry's Next Big Thing?

Another new powertrain technology may be poised to bring major change to the auto industry by delivering the advantages of hybridization without some of the complexity.

This technology, known simply as 48V, combines a dual-voltage setup with the well-known advantages of start-stop technology. By doing so, it more effectively captures a vehicle's braking energy, provides more power for a growing list of electrical loads, and simultaneously boosts fuel efficiency -- possibly by as much as 15 percent.

"We believe that, by the end of this decade, 48V will become a significant part of the market," Craig Rigby, vice president of product management strategy for Johnson Controls Inc. (which has developed a 48V product), told us. "It's probably the next technology after start-stop that will make sense for the mass market consumer."

Employing a dual-voltage architecture, Johnson Controls' Micro Hybrid battery system would use a low-voltage lead-acid battery and a 48V lithium-ion unit. The system could boost fuel economy by 15 percent. (Source: Johnson Controls Inc.)

If you're a bit skeptical because you think you've heard some of this before, you're not alone. During the late 1990s, auto industry executives talked up a technology known as 42V. After a few years of contentious debate, however, 42V died an inauspicious death. But suppliers say this technology is different; unlike 42V, it could offer a big jump in fuel economy. Moreover, the regulatory environment has changed, and battery technology has improved.

The 48V configuration, supported by a number of automotive suppliers, calls for a conventional 12V network using a lead-acid battery like those employed in most conventional vehicles. However, it adds an extra layer: a 48V lithium-ion battery with a separate 48V network. The 12V network handles traditional loads: lighting, ignition, entertainment, audio systems, and electronic modules. The 48V system supports active chassis systems, air conditioning compressors, and regenerative braking.

One of the keys to 48V is lithium-ion battery technology, which wasn't available at the time of the ill-fated 42V systems. Engineers say lithium-ion technology offers about three times as much energy density as lead-acid chemistry. "There's a size and weight advantage to using a lithium-ion battery," Rigby said. "Back in the '90s, we were looking at stringing three lead-acid batteries together to get that voltage."

More importantly, the 48V lithium-ion battery has more charging capability, making it a better candidate for capturing regenerative braking energy. "It really comes down to the notion of regenerative braking -- harvesting the kinetic energy from the vehicle during deceleration and storing it in the battery."

:-) I agree, and it's not always the best ideas that make it, only the ones that capture the imagination of the buyer/are better marketed (to a point). As a funny life experience with start/stop technology, in 1972 I had the clutch cable break on my 1965 beetle while waiting to drive on a ferry. I turned off the ignition, put it in reverse and turned the key then did the same in forward/reverse/forward again doing a 3 point turn and then proceeded to drive to a workshop by the same means. Once in first I could change gears by revving just the right amount AND THAT WAS A 6 VOLT SYSTEM :-)

but i do agree, even though every actual start/stop car I've driven this year has been a 12V system, charge recovery has to be better with higher voltages.

Someone will have to figure out at what fuel price point the expense of 48V etc. is justified.

If I may ramble on, I have often wondered about start/stop from an emissions and consumption standpoint, because a partially warmed engine uses about 20-30% more fuel, has significantly higher engine wear, and emissions are more difficult to control during warm up as well. This is partially because of catalytic converter temperatures. I know they can electrically heat them, but that's more fuel too, so I would be interested in knowing how much benefit there is if you're not stuck at a level train crossing for 10 minutes. I'm not saying stop/start isn't a good idea, only asking is it? and how good?

As you point out, there are a lot of very good reasons to question the viability of this idea, etmax. The one big thing it has going for it, though, is the inevitability of start-stop technology. Higher voltages are better for the operation of the starter-generator. And 48V lithium-ion is better at capturing that regen energy. As you say, it will be interesting to see (and if) this pans out.

Hi Charles, I often wondered why a technology (42V) that even Delco was touting as being the next big thing died, but at the end of the day it did add a lot of unnecessary cost at the time. Now 48V and a lithium battery it seems an even greater cost is being introduced, and given the deadly combination of a lithium battery and lots of falmmable plastics and fuel I thing the battery will have to be armour plated and placed within the confines of the passenger safety cell to avoid a catastrophe in an accident. Another show stopper I see is the LV directive that cuts out at 42V (possibly one of the reasons why 42V was chosen) so it will be interesting to see how it pans out. I don't think I'm going to hold my breath, as to me it looks like another attempt to sell a new idea for not too much added value. I've don't measurements on my car and the A/C uses very little, something around 1-2%

I don't think you can blame unemployment on current fuel prices, the US has very low fuel prices (based on global levels) yet has much higher unemployment. If anything that would indicate that high fuel prices lower unemployment. Of course that isn't the case either. What it is are 2 things, first there are not enough people earning enough money to be able to spend it in the wider economy therefore the economy is sluggish. If some of the money that is in the hands of the super rich and is spent on enormous mansions and $1000 handbags were distributed to the 30% of the population that can only afford to eat and shelter things would look better

The lithium ion battery technique will enable for the recapture of battery energy as it has been put by Charles. The use 48 V in the locomotives will no doubt lead to a cheaper and efficient method of locomotion. The answer to 48 V is therefore definitely a yes.

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